Visual Perception Flashcards
Process of Visual Perception
Explain the process of visual perception
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Sensation:
Reception (visible light spectrum): stimulus is recognised by photo receptors
Trandsuction (photoreceptors, receptive fields): stimulus energy is converted by the receptor cells into electrochemical nerve impulses
Transmission (visual cortex): Receptor sells send the nerve impulses to the primary sensory cortex where specialised receptor cells respond as the process of perception begins
Perception:
Selection (feature detectors): We can’t pay attention to all the millions of stimuli that we recieve at the same time, so we pick out the ones that are important to us and pay attention to those
Organisation: sensory information reaches the brain and is organised so we can make sense of it
Interpretation (visual perception principles): Our past experiences, motives, values and context (including stimulation) give the stimulus meaning
Biological Influences on Visual Perception
Determine the biological influences on visual perception
Physiological make-up: various physiological disorders are directly related to damage or impairment of structures in the visual system. For example (1) colour blindness/deficiency develops due to structural issues of the retina, in particular the cones; (2) congenital achromatopsia is lack of cone vision enabling an indidual to only see black and white; and (3) cerebral achromtopsia can result from damage to cerebral cortex
Aging: age influences both physical and psycholgical abilities, hence, the ability to percieve and interpret stimuli from the environment changes with age. Biological aging disorders include presbyopia (condition that develops as the lens looses elasticity and causes difficultied in focusing on close objects), floaters (clumps of matter that appear as small specks or spots in central vision), cataracts (cloudy spots in the lens that cause vision to become blurred when proteins in the lens break down), glaucoma (a disease affecting the optic nerve that interferes with the transmission of peripheral visual information to the brain), age-related macular degeneration (a build-up of grainy deposits in the centre of the retina causing deterioration of the central vision)
Genetics: Inherited visual disorders can be passed down from parents to their children due to genetic disorders. Common ones include cross-eyes, lazy eye, refractive errors and astigmatism. Some age related disorders - like glaucoma and macular degeneration can be attributed to genetic factors. (E.g. Retinis pigmentosa - genetic degenerative disease affecting the retina - causes night blindness and gradual loss of peripheral vision
Psychological Influences on Visual Perception:
Explain perceptual sets, the factors that influence perceptual sets and their influence on visual perception
Perceptual set: a predisposition to attend to (notice) certain aspects of a visual scene, or to interpret stimuli in a particular way according to certain preconceptions.
Factors that influence perceptual sets include past experiences (if the experience holds significant meaning, the same stimulus can be interpretted differently by different people), context (the environment in which a percieved stimulus is observed sometimes has an immediate effect on our expectations), motivation (we see what we want to see, e.g. if your hunry, you might see food ahead, when the sign said fuel ahead), and emotion (we can interpret someone’s facial expression depending on how we feel ourselves)
Fallibility of Visual Perception:
Explain the Muller-Lyer Illusion
Where a length, straighness, or parallelism of lines appears distorted in virtue of other aspects of the image (e.g. other background foreground lines, other intersecting shapes)
The Perceptual Compromise Theory
Fallibility of Visual Perception:
Explain the Ames Room Illusion
Where two people of the same size appear of vastly different sizes
From a particular perspective, the room appears to be a rectangle but is actually slanted, with object that are further away from viewer appearing smaller
Brain chooses to ignore human size constancy and instead focuses on room size contancy.
Fallibility of Visual Perception:
Explain the Ponzo Illusion
Absolute Threshold
Absolute Threshold - the minimum level of energy required for a stimulus outside our body to be detected by our internal senses. In ideal conditions, 50%of the time.
E.g. Hearing - ticking of a watch 6km away; Smell - one drop of perfume in a large house; Taste - one teaspoon of sugar in 10L bucket; Vision - candle flame 50km away
Define structure within the eyes: Sclera, Optic Nerve, Cornea, Aqueous Humour, Pupil, Iris, Lens, Ciliary Muscles, Vitreous humour, Retina, Blind spot, Rods, Cones
Sclera: Tough outer covering that gives the eye it’s shape
Optic Nerve: Transmits images received by the retina to the brain
Cornea: Curved; works with lens to focus images on retina; protects the iris
Aqueous Humour: Fluid that helps to retain the shape of the cornea
Pupil: Hole in the iris that controls the amount of light that enters the eye
Iris: Colored part of the eye; dilates/constricts to allow light into the eye
Lens: Hard, pearl-like structure; changes shape to focus images on retina
Ciliary Muscles: Attached to lens; change shape of lens to help focus images
Vitreous humour: Fluid in the main chamber of the eye; maintains shape of the eye
Retina: Receives light from environment; translates into nerve impulses
Blind spot: Lacks sight receptors; site where optic nerve attaches to eye
Rods: Perceive light impulses in dim light
Cones: Perceive colors; Long (red), medium (green) and short (blue)
Biological Influences on Visual Perception:
Describe the various biological influences on visual perception, including psychological makeup, aging, genetics, congenital visual disorders, and colour vision deficiency
Psychological Make Up
Various psychological disorders are directly related to damage or impairment of structures in the visual system. Eg. Colour blindness develops due to structural issues of the retina and it’s cones; congenital achromatopsia - lack of cone vision and only see in black and white; cerebral achromatopsia due to damage or trauma to cerebral cortex
Aging
Genetics
Inherited visual disorders are visual disorders passed down due to genetic disorders. E.g. cross-eyes, lazy eye, refractive errors and astigmatism
Congenital Visual Disorders
Colour Vision Deficiency
